In U.S. Pat. No. 3,583,550, issued on June 8, 1971, and assigned to the assignee of the present application, there is described a drive chain for transporting loads and the like. The drive chain described in that patent comprises at least two chains arranged in superposed interlocking relationship, with each chain having a succession of links with overlapping portions which are connected together by coupling members or pins. The drive chain therein described constituted an improvement over the drive chains which theretofore had been used for transporting loads and the like. For example, as disclosed in that patent, in the prior art transport devices including drive chain systems, each chain or chain pair has exclusively associated therewith guide and drive members. Frequently, space and equipment limitations limit the number of chains that can be employed. Moreover, the load-carrying capabilities of such drive chains are limited. Since, generally, the load is carried by the pin members of the chains which connect the links of the chain together, and these pin members have limited shear strengths, care must be taken to avoid shearing the pins due to overloads.
Although the drive chain described in the aforementioned patent affords some improvements, it nevertheless has limited load-carrying capability.
Accordingly, it is an object of the present invention to provide an improved drive chain which is capable of transporting larger and heavier loads than the prior devices, including the drive chain described in the aforementioned patent.
It is a further object of the present invention to provide a drive chain wherein two pairs of chains share one sprocket during their travel, one pair running inside, and the other pair running outside the inner pair.
It is still another object of the present invention to provide a drive chain system comprising a plurality of chains and sprocket means cooperating to maximize the load-carrying capability of the system.